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Fungus Gnats


Fungus Gnats

Usually appear in

All year

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Caused By:-     Many Genus and species of the Order Diptera


Fungus gnats are small black flies(around 2mm), which are also known as Sciarid Flies or mushroom flies.They are a common pest on or near the surface compost of houseplants. They run over the soil surface or fly slowly around plants in pot and in borders. Their presence is usually indicative of more serious problems with the plant husbandry especially as they are attracted to damp wet soil where they lay their eggs. This usually means over-watering. The maggots are difficult to see with the naked eye due to their small size and translucent bodies. Some species of Fungus gnats do not cause damage, but some can cause damage to seedlings, cuttings and other young plants by eating the roots and shoots or boring into the stems of cuttings. They feed mainly on plant materials, but are also partial to any form of decaying organic matter. Picture by Whitney Cranshaw, Colorado State University,


Allow the surface of composts to dry out a little before watering the plant again. Remove dying leaves and dead flowers regularly, so that they do not begin to decay and so attract the gnats. Adults are less likely to lay eggs on dry surfaces with no decaying plant tissue for the newly hatched maggots to feed on. Therefore covering the compost with grit can help by stopping their attraction to your prized plant. Sticky Yellow Traps are a good idea in the greenhouse and indoors if practicable, for they trap a large number of the gnats and other flying insects that may be troublesome, such as whitefly and flying Aphids. There are several biological controls available some of which are the predatory mite, Hypoaspis miles and H. aculeifer that lives in the surface layers of compost and will feed on the maggots if the temperature is kept at around 21 ?C., The ‘hunter fly', Coenosia attenuata, The parasitic wasp, Synacra sp., The ground-dwelling predatory ‘rove' beetle, Atheta coriaria, The predatory mite Macrocheles robustulus, The nematode Steinernema feltiae and Heterorhabditis bacteriophora and Watering with a solution of Bacillus thuringiensis, an organic control for caterpillars, to kill gnats larvae. Bacillus thuringiensis is a bacteria and is safe to use around children and pets.

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